create ev3dev-buster branch

[dwalton76]

Once we have figured out what to do with these formatting PRs:

• format code via yapf #716
• format code via black #713

we should pull an ev3dev-buster branch and re-submit the #709 PR to be against buster since it is a breaking change.

[WasabiFan]

@dlech What are the general expectations for Buster? It it worth releasing versions for Buster, or is Stretch expected to live on for a while as the primary platform? I was under the impression it was the latter -- if we made Buster-specific releases I wasn't imagining people would actually see/use them.

[dlech]

I did some work on the kernel a few months ago, so buster should be in pretty good shape. So I wouldn't be opposed to listing it as beta on the downloads page if we want more people to see it. I was hoping to also do some work on boot time and long standing brickman bugs before really promoting it, but haven't really had time for that.

[WasabiFan]

I didn't comment this explicitly before but based on what you said my thinking is that this library doesn't have a strong motivation to release a Buster-specific version yet but that doesn't mean a Buster release overall would be bad.